Chlorine dioxide (ClO2) is a gaseous sterilizing agent used as a bactericide, viricide, and sporicide. Chlorine dioxide is also an effective microbicide in solution that can also destroy many chemical substances and toxins. Chlorine dioxide has excellent environmental qualities, as it does not produce large quantities of chlorinated hydrocarbon byproducts. Generally, the stability of ClO2 solutions does not lend itself to long-term storage. For this reason, chlorine dioxide solutions are generated immediately before use.
Many processes, such as electrolysis and chemical mixing, are known for the production of ClO2 in gas or solution forms suitable for large-scale use. Usually, sophisticated equipment and significant amounts of power are needed to produce ClO2 by electrolysis of chlorite solutions. When prepared chemically, the reaction components must be maintained separately until mixing for the production of chlorine dioxide.
Chlorine dioxide solutions can be produced by treatment of chlorite salt solutions (e.g. NaClO2) with a strong acid (for example, sulfuric acid) to produce acidic solutions that contain ClO2. Ion exchange media can be used for the formation of chlorine dioxide; for example, U.S. Pat. No. 3,684,437 to Callerame discloses production of chlorine dioxide by ion exchange between a mixed bead cation-anion exchange resin and a chlorite of an alkali metal or an alkaline earth metal with a very slow flow rate. Similarly, U.S. Pat. Nos. 7,087,208 and 7,824,556, both to Sampson et al., disclose generation of chlorous acid from a chlorite salt precursor by passing an aqueous solution of the precursor through a cationic ion exchange resin in a hydrogen ion (acid) form and a catalytic material to accelerate the decomposition of chlorous acid to chlorine dioxide using gravity feed at a moderate rate.
More recently, U.S. Pat. Nos. 7,964,138 and 8,323,563 to Richardson et al. have disclosed chlorine dioxide generation with a generator that uses a chlorite bound ion exchange resin with an acid feed solution or an oxidant feed solution, such as, aqueous chlorine or bromine. Furthermore, U.S. Pat. Nos. 7,964,138 and 8,323,563 describe use of an oxidant bound ion exchange resin, for example, a Br3− bound resin, and a chlorite feed solution. The generator based on these patents can be portable for the production of chlorine dioxide solution on demand at a reasonably rapid controlled rate.
Although the method of Richardson et al. is useful for commercial and even portable emergency production of chlorine dioxide, the containment and storage of a relatively large amount of an isolated aqueous solution as the feed solution is required. Therefore, a method of retaining both complementary reagents in a bound state, such that any available water as the liquid feed, rather than a specific precursor-containing solution, would be desirable to reduce the complexity and volume of a chlorine dioxide generator. A first bound reagent would be situated upstream of its complementary second bound reagent, and would need to be in a state where the first bound reagent could be dissolved into an aqueous solution in a controlled manner. The total quantity of the first reagent must not be passed immediately from the system and the desired chlorine dioxide solution should be of a nearly constant concentration over a practical period of discharge.